1. Field of The Invention
The present invention relates generally to a piston. Particularly, to a piston for an internal combustion engine which is provided with a knock pin located in a bore provided in the face of a piston ring groove.
2. Description of The Background Art
Conventionally, pistons for internal combustion engines have been proposed which utilize knock pins for preventing rotational movement of a piston ring. One such conventional piston is disclosed in Japanese Patent Application (First Unexamined Publication) 59-215942. This document relates to an aluminum alloy piston provided with a knock pin opening in the bottom of a circumferential piston ring groove. A tail end of the knock pin is fitted into the opening and a head end engages with portions of a piston ring, to prevent turning or rotation of the piston ring.
With this arrangement, factors such as movement of the knock pin within the knock pin bore as well as engine running duration, temperature and piston expansion, cause stress to be applied to the knock pin, particularly to the head end, resulting in repeated springback of the knock pin according to changing operating conditions. This can lead to breakage or deformation of the knock pin.